class testStudent {
    public static void main(String[] args) {
        Student stu = new Student();
        System.out.println(stu.name);
        System.out.println(stu.age);
        stu.name = ("张三");
        stu.age = 23;
        System.out.println(stu.name);
        System.out.println(stu.age);
        stu.study();
        System.out.println(stu);
    }
}
    public class Student {
    String name ;
    int age;
    public void study(){
        System.out.println("学习");
    }
    }
